Fish emulsion has higher levels of nitrogen which pumpkins need lower nitrogen and higher levels of phosphorus. Fish emulsion might be okay to use in the early stages to promote leave, root, and vine growth but afterwards when blossoms are appearing I would stop using something that has so much nitrogen in it and use something that has stronger phosphorus. I used fish emulsion in the very early stages and now morbloom on my fairytale, cinderella, and jack o' latern variety pumpkins which is 0-10-10 and it works well for me. Very healthy plants, or something like 5-15-15 might be ok too. Hope it works out for you!

I meant to type 5-15-5, 5-nitrogen 15-phosphorus 5-potassium, my soil is also rich in micro nutrients and minerals and they do fine.